I recently bought another android device. How to add my 2nd number to Google play account? So that, I can easily choose to install apps from google play into my 1st number or 2nd number.
Google Play is not tied up to phone numbers, but to Google accounts.
Just add/sync your existing Google account into your phone via
System Settings > Accounts > Add Account. You will then be able to download / use the paid apps that you had in your other phone, assuming they are compatible with your second phone.
Then from Google Play, just select the account that you'd like to use.