My friend and I were denied a UK visit visa to attend an on-site interview for a tech company

With the addition of the refusal notice, I took the liberty of editing your question, for clarity, correcting the terminology (refused, not denied, per UKVI usage). Also, it’s impossible to respond to your friend’s circumstances. While you both applied, and for the same reason, you cannot place two applications side-by-side, and draw the conclusions as you are. Applications are assessed on a first-principles basis; while both were refused and, perhaps, for similar reasons, it’s impossible to offer a cogent response here.

Yes, you are correct, the UKVI does often cite specific paragraphs of the Immigration Rules and, when it doesn’t, it suggests considerable issues overall.

V 4.2 Genuine intention to visit: "It is the intentions of the application that are paramount…. " What you provided, and what may have been missing, failed to convince the ECO, full stop.

The refusal suggests concerns under sections V 4.3 and V 4.4. When funds, maintenance and accommodation is provided by a third party, you have to present solid evidence that there is a genuine relationship (in this case, professional) and a valid written undertaking.

Ascertain whether the company with which you would interview has has a sponsor license and is in good standing with UKVI. You can do this at the register of licensed sponsors: workers. The document lists Tier 2 and 5 sponsors, the category of workers it’s licensed to sponsor, and it’s sponsorship rating. This is essential to your premise for entering the UK, and the ECO will verify the organisation’s standing (and may have done so in your recent application).

Your premise for entering the UK was not believed: citing all the additional sections simply highlights the failure to satisfy the ECO, pointing to potential visa violations (work, study, access healthcare or marry).

Without agonizing over each of those, and arguing that was not what you intended, it would be better to attend to the shortcomings.

• Verify that the company is entitled to sponsor, and your candidacy for a position. And if the company is not, or has a poor rating, or your qualifications are inconsistent with its stated purpose, a second application would not succeed.

• Provide evidence about your studies, qualifications: include course of study, when you will graduate, with what certificates/diplomas, confirmation of enrolment. This is essential, when the potential outcome of the interview would be to enter the UK to work; without requisite education, skills, training, such an interview would be fruitless, as would an application is another visa category.

• Document your finances (sources, including monies from UK company, and that you have access to the funds; your father’s source of income from his employer etc). It’s not that the ECO would be satisfied by a letter from your father, the ECO needs to see that the funds are legitimately obtained, that a certain sum is there for your use. It’s not unreasonable that a student has parental support; what is irregular is when a unreasonable portion of that income would be expended on a short trip. Having the company indicate full support and then adding that your father will undertake the same is conflicting, and confusing.

• Bank statements: you added information on what you had provided as part of the refused application and as you describe those, on the face of it, may require evidence to support the account activities (particularly loans, monies in other currency, transfers). Review the TSE canonical on bank statements as it can guide you on how to navigate that issue.

Be patient as you go, as you would not want to invite a second refusal, particularly if you wish to work and live in the UK. This additional TSE canonical on supporting documents may help.

As noted, I did edit out the bits regarding your friend's refusal as it isn't relevant to yours. Rather, it is a separate question, but may be satisfied by the above, as well as the discussion found in the TSE canonical: UK visa refusal on V 4.2 a + c (and sometimes 'e').