Sequece of Meditation and Side Effects

Question 1: Does side effects occur due to basic or minimum of Buddhism Precepts or Sila (requirement) not been achieved yet?

Yes. Right speech, right action, and right lively hood are all foundational virtues. If your morality is not in check, the mind tends to be busy. The side effects that occur due to the above precepts not being adequately followed include but are not limited to gilt, anger, fear, worry, frustration, and the cultivation of complicated and trouble causing situations.

The reason why they suggest tackling the above before meditation, is so that you can stay focused. It is easy to be distracted if you try to meditate when, due to poor morality, you have cultivated pervasive mind states.

You could still meditate before getting your life into a peaceful state, but you make more work for yourself if you don’t.

Question 2: As a lay Buddhist, is it a right practice if the sequence is wrong or Sila/Precepts and Meditation being practiced together? If no, then at what stage of requirements? Well, i know at least not after being drunk and go meditate.

As a lay Buddhist, the order doesn’t really matter. The order only matters if your goal is to become enlightened. Each layer makes the next one easier to achieve. By having good morals it becomes easier to meditate. By meditating you train the mind to be more able to observe the universe as it is and gain wisdom.

If you are meditating for some other reason than to train the mind to cultivate wisdom, such as to de-stress or energize the body, just make sure you set the right environment to achieve what you are looking for. If your goal in meditation is to enhance concentration, don’t drink beforehand. If your goal is feel peaceful, don’t murder someone the day before.

Just know if you don’t follow the suggested order, the next link in the chain will be harder to achieve.

Question 1: Does side effects occur due to basic or minimum of Buddhism Precepts or Sila (requirement) not been achieved yet?

Yes.

However, the minimum Sila is not just 5 precepts. It is included "good verbal&bodily behaviors" and "the virtue that has livelihood as eighth" (7/10 of Paths of Wholesomeness with right livelihood).

For example, if one can keep in 5 precepts, but he never taking care of his mothers, his wives, or he is stubborn to the Buddhist masters, then he is breaking the virtue in MangalaSutta, etc.

Question 2: As a lay Buddhist, is it a right practice if the sequence is wrong or Sila/Precepts and Meditation being practiced together? If no, then at what stage of requirements? Well, i know at least not after being drunk and go meditate.

The sequence is not depending on completion because the completion is at the enlightening moment. It's depending on the knowledge accumulation (paññā > ñāna > purification) and each time renewal attentions (samādāna). When you are keeping your virtue on the right knowledge, or developing your knowledge then renew your action to be better. This is enough virtue for the meditation. However, this is just what identifying that you can do the meditation. It is not guaranteed you are going to enlighten. If your virtue and concentration meditation is not good enough, your insight meditation will not get the enlightenment state.

So, keep meditation, keep goig to meet the Tipitaka Memorizer master, such as Pa-Auk Tawya Sayadaw, keep reciting and memorizing Sutta and it's commentary more and more to keep meditating your knowledge.

And don't trow away them entire your life because you are practicing your behavior and we keep the right behavior entire life or until it is wrong.

Ps. The meditation is development. The good development is the continuous doing without any space in between. Some project developers drink alcohol to depress their confusing mind while doing a project. But the Buddhist practitioner can't drink it because we are practicing the awareness of unwholesome by keeping mindfulness wholesome, so if we drunk we already destroyed our meditation.

Do you the concentration meditation instead to depress our mind after the insight meditation.

The Kimattha Sutta (AN 11.1) -- says that the purpose of "skilful virtue" is to lead, via "freedom from remorse", through other states of mind and ultimately to knowledge and vision of freedom.

This is close to what you're asking, except that it focuses on "good effects" instead of "unpleasant side effects".

See also one of the answers to What is the basis? which says,

So the absence of remorse is conditioned, but not being an existing thing, not having been constructed (sankharaed)-- it was the result of not-doing, is not itself subject to ending and is a small taste of Nibbana.

I think that's difficult for "worldlings" to understand. A worldling will delight in what exists, and in what becomes. Conversely an ariyasāvaka may esteem what isn't subject to becoming -- e.g. in SN 36.6:

Because an educated noble disciple understands an escape from painful feeling apart from sensual pleasures. Since they don’t look forward to enjoying sensual pleasures, there’s no underlying tendency to greed for pleasant feeling underlying that. They truly understand feelings’ origin, ending, gratification, drawback, and escape. There’s no underlying tendency to ignorance about neutral feeling underlying that.

AN 6.10 says that "recollection (or remembrance) of own virtue" -- as well as the other recollections, including "recollection of generosity" -- is an basis for concentration:

Furthermore, a noble disciple recollects their own ethical conduct, which is unbroken, impeccable, spotless, and unmarred, liberating, praised by sensible people, not mistaken, and leading to immersion.

I think that what I said about the problems of a "worldling" is crucial. It reminds me of how difficult people say it is to explain enlightenment in a way that unenlightened people can understand. I think that Mahanaya has a metaphor of the finger pointing at the moon with "the moon" being a symbol for enlightenment.

With that in mind I read The Moon Cannot Be Stolen