What can be deduced from the Gospel of John about prayer?

I found a few studies on Jesus's prayers in the Gospel of John, especially about the Farewell Discourse (John 14-17).

• 2020 Journal Paper by Scott Lewis Adams Prayer in Johannine perspective : an analysis of prayer in the Farewell Discourse and 1 John.
  From the Abstract:

  ... This work seeks to analyse ... the prayer passages located within the Farewell Discourse (14:12–14; 15:7–8, 16; 16:23) and 1 John (3:21–22; 5:14–18). This article begins by exploring how the Farewell Discourse prescribes prayer as the means by which greater works will be performed and much fruit produced in Jesus’s physical absence. Then attention is given to demonstrating that the author of 1 John, dissatisfied with the prayer tradition in the Farewell Discourse, provides a nuanced account that focuses on how confidence in prayer relates to real-life, ethical scenarios within the community he addresses (3:11–24; 5:14–17). Finally, this article concludes by arguing that the discussion of prayer in 1 John 5:14–17 is more concerned with the preservation of the believing community than its numerical growth. Attention will be given to analysing the prerequisites, privileges and purposes of prayer in both documents in order to provide a more complete, nuanced profile of Johannine prayer. ...

  From the Conclusion:

  In this brief analysis, I have sought to compare select prayer passages in the FD with those in 1 John for the purpose of offering a more complete, nuanced profile of Johannine prayer. While the Fourth Gospel contains five instances of Jesus praying to the Father, I have narrowly focused on the prayer passages in John 14–16, discussing their relationship to prayer in 1 John 3 and 5. Following Von Wahlde, I have argued that it is possible that the author of 1 John was not satisfied with the prayer tradition of the FD and therefore sought to provide an expanded, nuanced account concerning the conditions and outcomes of prayer. Notwithstanding, both documents highlight the assurance one can have in prayer—whether one prays for the numerical growth of the community or its ethical and confessional fidelity—and they do so in a complementary but differently nuanced manner. Whereas John 14:1, 12–14 and 15:1–7 put forward belief in Jesus, the efficacy of his name and abiding in him as the grounds of one’s assurance in prayer, 1 John embeds the topic of prayer in real-life, ethical scenarios that illustrate how such existential confidence in prayer is achieved. Obedience is not the ground of one’s confidence in prayer, but is rather the fruit of one’s union with Jesus, which is made possible by his atoning sacrifice. But the one who abides in the sphere of love will bear the fruit of love as he imitates Jesus’s character. While confidence in prayer is implied in John 14:13–14 and 15:7, it is explicitly stated in 1 John 3:21–22 by the author’s usage of παρρησία. Hence, the FD and 1 John employ slightly different vocabulary, but envisage the same optimistic outcomes for prayer. As far as 1 John is concerned, one can pray confidently for a brother (or sister) who is committing a sin that does not lead to death. While the nature of such sinning is not specified, the author of 1 John clearly indicates that the believer’s prayer is the means by which a brother (or sister) is restored to life.

• 2020 Book by the same author, Scott Lewis Adams, Prayer in John's Farewell Discourse: An Exegetical Investigation.

  From a review:

  ... Adams surveys the practice of prayer in Jewish, Greco-Roman, and Christian contexts before turning to the Gospel. His analysis of John 14-16 demonstrates the importance of locating prayer in a 'relational space, ' i.e., prayer in Jesus' name. Adams establishes connections between prayer and important Johannine themes, especially friendship, knowledge, fruit-bearing, and frankness, and shows how these themes are rooted in the Hebrew Scriptures. ...

• A 2018 Book by D.A. Carson: Farewell Discourse and Final Prayer of Jesus: An Evangelical Exposition of John 14 - 17 (Excerpt containing TOC and Prologue here). From the back cover:

  What can we learn from Jesus's final teachings before he went to the cross?

  In this illuminating study of John 14-17, D. A. Carson unpacks Jesus's message to his disciples after the Last Supper, in which Jesus proclaims the coming of the Holy Spirit. Carson explains Jesus's teaching on the coming and the work of the Holy Spirit, as well as his commandment to love one another. He also offers insight into the high priestly prayer, in which Jesus prays for himself, for his followers, and, ultimately, for us.

• A 2004 paper by Dorothy Lee In the Spirit of Truth: Worship and Prayer in the Gospel of John and the Early Fathers.

  From the Abstract:

  The Gospel of John had a powerful impact on the early Church not only in its theological understanding of God but in its conviction of the centrality of worship. In the Fourth Gospel, worship is made possible through the Spirit who gives birth to believers, making them children of God and participants in Jesus’ own filiation. The Johannine Jesus, through the Spirit, becomes both the locus and object of worship, the source of worship as well as the true worshipper. This understanding is the ultimate source of the Nicene Creed’s assertion that all three Persons of the Trinity are to be ‘worshipped and glorified’.

  From the Conclusion:

  It would be anachronistic to employ uncritically the language of later centuries to describe John’s theological reflections on worship and prayer. Yet from the second century onwards, the language of liturgy, apologetics and credal formulation in the early Church upheld the biblical witness to the oneness yet plurality of the God revealed in Jesus. These centuries owe perhaps more to the Gospel of John than any other New Testament theologian (with the possible exception of Paul). In a forum such as this, honouring the scholarly work of Eric Osborn, it is permissible to move freely across canonical boundaries to the biblical and theological reflection of the early Church. Professor Osborn’s work, spanning several decades, interprets the writers of the second century in particular within such a biblical and theological framework. In one sense, therefore, we are free to speak of the Fourth Gospel as trinitarian in its understanding of worship,⁷² a Gospel that in any case “stresses the unity of three persons”,⁷³ even if the distinctions are not as fine or lucid as they become at Nicæa. In different ways, John’s Gospel expresses the unity and reciprocity of Father and Son who are the object of the believing community’s worship.⁷⁴

  Yet the Nicene Creed declares that the Church worships and glorifies all three Persons of the Trinity. The mutuality within the Johannine Father- Son relationship includes, by extension, the “Spirit of truth” who in the absence of Jesus leads the believing community “into all truth” (16:13). It is through the Spirit, êllon parãklhton (“another Paraclete”, 14:16), operative in the life and death of Jesus, that human beings are empowered and directed to offer authentic worship to the Father. The Spirit shares with Jesus the task of both convicting the world of sin and revealing the truth, thus making present the indwelling of God. True worship is possible only in the power of the Spirit who gives birth to believers, making them children of God, participants in Jesus’ own filiation. As revealed to the receptive Samaritan woman, Jesus is the locus and object of worship, the source of worship and the true worshipper, the bridge between heaven and earth,⁷⁵ the one whose search for true worshippers is the expression of the Father’s love and longing. Worship and prayer are to be offered through Jesus but also, since he is the visible manifestation of God, to him.⁷⁶ In his flesh the worship he embodies is the symbolic enactment of both self-offering and mutual glorification, the source—through the abiding presence of the Spirit-Paraclete—of the believing community’s life and worship.