Euphyllia Glabrescens, Looks like it could called an Indo Gold 24K, which are also sold under several namesakes by the vendor who is selling them. With torches there can be some variance with tentacle structure but much depends on the flow it is exposed to. Slower oscillating currents will help to stretch them out longer and stronger turbulent flow will often result in shorter tentacles within the same sub species. There are some short fat tentacle variants in the hobby but this does to appear to be one from any of the pictures you've shared. The shortening of tentacles is somewhat a means of protection. During rough and/or direct forceful current they will shorten. Stronger flow and especially direct forceful flow can push/pull the tissue away from the skeleton causing polyp bailout. This "harder" flow cause damage from the tissue pushing against the sharp corallites just below the tissue which can allow bacteria to enter the tissue through the abrasion(s) and cause infections which can quickly lead to death.
Maybe more/different info than you were looking but figured if you were looking to lengthen the tentacles or keep them shorter like they appear now know what to expect from the flow patterns would be helpful.
