Hi Gilcemar ;

• No .. that is governed by the Transaction object which is instantiated uniquely (has it's own O/S "handle) within each the App's "address space" which cannot be shared.
• Yes ... if you use PB's Multi-threading feature as the "main" thread can connect & then pass the address of the "active" Transaction Object (own O/S "handle) to the other sub-threads to use.
• Alternative #1 .. use DB Client's "Connection Pooling feature" (if it supports it).
• Alternative #2 .. use PowerServer's "Connection Pooling feature". 

HTH

Regards ... Chris