FLR m Extension but no proof to show cohabitation( Living together) etc

Hello Dear Casa, CR001 and everyone,!
I have some more questions regarding extension of my spouse visa. if u can guide plz.
1. my and my daughter( dependent) spouse visa will expire on 16 feb2022.it was granted on 15 may 2019,i enterd Uk on 13 June 2019 and my daughter entered on 11june 2019,i want to know if the expiry date on biometric card will be counted for 28days rules or the date we entered Uk?

2.I have nothing in my name here as everything is in the name of my mother in law, so is a letter from her is sufficient to say that we are living together with her on same adress..? I got only 1,or 2 GP letters or sim card letters on my name in last 2 years.
Does a single/joint account (me and husband) will be ok to show cohabitation?How much period should the bank statement covered?
Plus our daughter is also on dependent visa what should we need for her to show that she is living wd us?
3.My husband was abroad for long period for some personal work, in2020.can it effect on our subsisting relationship requirements?