Yes, you can pull up all the jacks and the front jacks will support the camper just fine.
Now, here's something you can do. Raise all the jacks and leave the front down. Now, put blocks, or bricks under the frame of the camper near the front jacks and lower the camper onto the jacks and you can raise the front one too. Now the front of the camper is resting on the blocks and ALL the jacks are up. This is how you re-home all 6 jacks when they throw an error so you can lower them all 6 inches, then retract them all at the same time. Otherwise, you have to hitch up to the truck.
Anyway, it's just an option you might consider. But, the jacks are made to support the camper from the front. No problem long term or short term either.
I used floor jacks here in these images, but I still prefer using solid blocks of wood.
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2019 Montana High Country 375FL
2014 Chevy Silverado Duramax, 6.6L Dually