Thank you for your reply.
I logged in using Eva's confirmation number on Eva Airways website and was able to see my seats on my desktop.
I am glad the seat will stick bcos UA CSR wasn't sure and insisted that my seat was not chosen.

I am not able to select my meals yet till Oct 1st according to website. Do you have any meal type to recommend? Many thanks!

I figured I will have to go to the Polaris lounge till late to get over to the T5.
Will be my first time going to a Polaris lounge. I supposed I just need to show them my boarding pass like with AA.
Upon checking I see the Polaris location is at Concourse C C18.

Which lounge did you use at T5? Yes, the wait is going to be long at T5 unfortunately.

Good to know that there is an airside bus so I don't have to go thru security again at T5.

So appreciate your reply!