opatch is utility to apply database patches
Q. Can you use both adpatch & opatch in Apps ?
Yes you have to use both in apps , for apps patches you will use adpatch utility
and for applying database patch in apps you will opatch utility.
Q. Where will you find forms configuration details apart from xml file ?
Forms configuration at time of startup is in script adfrmctl.sh and
appsweb_$CONTEXT_NAME.cfg (defined by environment variable FORMS60_WEB_CONFIG_FILE)
for forms client connection used each time a user initiates forms connection.
Q. What is forms server executable Name ?
f60srvm
Q. What are different modes of forms in which you can start Forms Server and which one is default ?
You can start forms server in SOCKET or SERVLET by defualt Forms are configured to start
in socket mode.