Ye shall receive (apolēmpsesthe). Future middle indicative of apolambanō, old verb, to get back (apo), to recover.
The recompense (antapodosin). “The full recompense,” old word, in lxx, but only here in N.T., but antapodoma twice (Luk 14:12; Rom 11:9). Given back (apo) in return (anti).
Ye serve the Lord Christ (to Kuriōi Christōi douleuete). As his slaves and gladly so. Perhaps better as imperatives, keep on serving.