I will do a real time PCR using taqman assay for a specific microRNA.

I am very confused about the best master mix to use.

I found that taq-man has 4 master mixes;

1-with no Ampearse UNG

2-with no UNG

3- with Ampearse UNG

4- with UNG

I am specifically confused about the difference between the first two master mixes?

Also, i heard that expired kits can work in some cases. And I found in my lab a taq-man miRNA reverse transcription kit expired from 2015, can I still use it ? And if I used it, how can I know wether or not it worked ?

Thank you in advance