What is the ruling on performing istinja' before every ablution?
Istinja' is not from the conditions for the validity of ablution. It is only obligatory for prayer when there is impurity from urine or stool on the private part, or if there is fear of the impurity spreading to the body or clothing. And Allah the Almighty knows best.
Is it permissible for a wife to boycott (not to attend to his different needs) her husband?
It isn`t permissible for the woman to boycott her husband unless he is the reason behind that, and it is recommended that both spouses seek the advice of righteous people to make reconciliation.
What is the ruling on congratulating others on the arrival of Ramadan?
Congratulating others on the arrival of Ramadan is permissible.
If someone does it to express their love for worship and the blessings of Ramadan, and congratulates their fellow Muslim, they have done something good.
The Prophet ﷺ said: "Shall I not tell you something that, if you do it, you will love one another? Spread peace (Salam) among yourselves." [Narrated by Muslim]
Giving Salam is a prayer for peace and safety.
What is the ruling of Islamic Law on a fictitious marriage for the purpose of obtaining citizenship?
All praise is due to Allah, and peace and blessings be upon our master the Messenger of Allah ﷺ.
There is no such thing in our noble sharīʿah as a "nominal" or "fictitious" marriage or divorce. Marriage and divorce are among the sacred ordinances of Allah, and it is not permissible to manipulate them or use them as a stratagem to obtain worldly gains.
The foundational purpose of a marriage contract is the permanence and continuity of the relationship between the spouses — to establish a family, and to bring forth righteous offspring. So sacred is this bond that Allah the Almighty Himself described it as a solemn covenant (mīthāq ghalīẓ), saying {what means}: "And if you wish to replace one wife with another and you have given one of them a great amount of wealth, do not take any of it back. Would you take it in injustice and manifest sin? And how could you take it while you have gone in unto each other and they have taken from you a solemn covenant?" [Al-Nisāʾ/ 20–21]
Accordingly, it is not permissible to resort to manipulation and deception in contracts that Allah, Mighty and Majestic, has described as a "solemn covenant" — all for the sake of material and worldly benefit. Marriage is built upon permanence and does not admit of a fixed time limit. If a time limit is stipulated in the contract, the contract is rendered invalid by the consensus of the jurists. Similarly, marriage is impermissible when there exists a mutual, concealed intention to limit its duration — even if no time limit is explicitly mentioned in the contract — for this constitutes a form of unlawful circumvention of the sharīʿah. This is to say nothing of the lying and deception that such conduct involves, the prohibition of which needs no elaboration. Lying, deception, and fraud for the purpose of obtaining worldly gains are among the gravest of sins.
If, however, the marriage contract is first concluded in a valid sharʿī manner and then registered civilly, it is sound and fully valid. And Allah the Almighty knows best.