replacing flange on copper pipe

I'm in the early stage of a bathroom remodel & need to replace the toilet flange. I'm trying to figure out how the flange is attached (glued, sweated, other) & the best way to remove it. I'll have excellent access from both top & bottom as I'm taking the original floor off right down to the joists & on the bottom I just had to remove the dropped ceiling from the downstairs bathroom. All the piping is copper in excellent shape including the bend. Ideally, I'd rather not cut out the bend as I'd hate to cut out perfectly good copper pipe, but will if I have to. Any advice is greatly appreciated.

Terry,
Thanks for your quick reply. After removing the remaining subfloor & throroughly cleaning the flange, it turns out the flange is in good condition. Also, I'm not sure how common my situation is but the flange is copper also.

flange

A lot of heat from a good torch will get it hot enough so it slides off.

hj,
Even though the flange appears to be in good shape. It's still the original one installed 37 years ago. Would you recommend removing it anyway. Thanks.

flange

Remove it if you have, or want, to change its height. Otherwise use wax rings to adjust for differences unless it will be too high.