Questions about HDFC Regalia Lounge Access Voucher / Other cards lounge queries too

I have HDFC Regalia card (not regalia first, not even sure if it is some different card). I understand that the TnC have changed w.r.t lounge access and now the requirement is to have minimum spend of 1L in one quarter to get the access. Based on that, I get 2 vouchers of lounge access from what I read.

So i went to the smart pay regalia page and do see that due to my oct-2023 to dec-2023 spends, I am eligible for 2 vouchers. I have not availed it yet but I am going to travel soon domestically and would like to use the lounge in Mumbai. Here are some questions..

1. Once i have generated the voucher on smartbuy, for how much time is it valid? I am not risking and generating it now and planning to do it like a day before the travel date, is that ok?
2. Since I have 2 vouchers that I can redeem, if I do so, can I use both vouchers together? Like one for my entry and one for my wife's entry into lounge?

1. I have Tata Nue Infinity HDFC RuPay card which also provides lounge access at airports. Is there minimum spend requirement too for this card? I did not find any such thing.
2. I have Scapia / IDFC First select Visa signature credit cards and both have a minimum 5000 rupees spend. My question is, the lounge access we get after spending 5K on these cards is valid only for like next month until next billing cycle or it has more validity? I am unable to understand this "spend this month, get lounge access next month" as billing cycles can be different for people.