But my intentions are to know them better. I mean through Visual FoxPro and Spt. What does the second Instance do in case of the first having a lock and then lossing the connection midway?
Right. first instance can do nothing but does the sqlserver still hold the lock and still is not avaiable for the second instance?

no, SQL Server have a "connection live" monitor,
if the connection is lost SQL server release all the resources of the connection,
and locks are removed.

You can use the T-SQL command:

SET LOCK_TIMEOUT 500

and manage the lock error 1222
for cancel/message/reprocess ... the SQL command

Fabio