Hi @mo -
Whilst @10x is correct in the fact that you should not make your SET(LR) application 70 days in advance of meeting the 10 year qualifying period, due to the fact that the application reach a caseworker and be considered before you are eligible, they are incorrect in saying that you should make a FLR(LR) application.
The main requirement of a FLR(LR) application is still that you must have spent a minimum of 10 years continuous residence in the UK.
This being the case, I will answer your questions in turn:
You should not do this and the Home Office wouldn't give any regard to your cover letter asking for a delayed decision.
I am unable to provide you with an estimate on the chance your application will be granted as I do not know your immigration history and the supporting documents that you will be submitting.
Same as ''2''
For SET(LR) applications the date that the application is considered is the date that they will work with, therefore, if the application wasn't picked up until after the 70 days, you would meet the 10 years residence.
As long as you meet all of the other requirements then that is correct.
Yes, this is possible but would need to be handled carefully.
It is also worth noting that you are able to apply up to 28 days before you meet the 10 years continuous residence, if you have not taken this into account then it does mean you would only be 42 days short.