Can we store the authorize code and can use in future after allowing application with infusionSoft to generate the access token as every infusionSoft Api request requires access token?
That is the recommended approach. You have a user authorize once and then it returns a pair of tokens (and access token and a refresh token). Store those with the date/time and run a process once an hour that will use the refresh token to get a completely new pair of tokens and store the new ones in place of the old ones. The refresh token is good for six months but the access token is only good for 24 hours, so the process that runs every hour would check the time left and around 20 hours in (4 hours left) start trying the refresh process. That way, if anything fails for any reason, there are a few opportunities to retry it before it expires. I have a video on this which I’ll link to below for you 
