Can I use the old iCloud account of my previous phone if I open new phone with new apple id ?

No. iCloud accounts are not tied to any one device. They are tied to the AppleID used to make them. If you make a new AppleID and use it with iCloud then you’ve also made a new iCloud account.

To use the same account on multiple devices, just use the same AppleID on all devices.

Login with the 'old' iCloud account.