Honda mower trying to ID age

I just came into possession of a nice older Honda mower model: HRX217 HMA, the frame serial is MAGA 1128330 and the engine serial is GJAAA 8003749

A) I cannot find out the approximate age of the mower (I know they don't date their products by year). It seems in nice shape despite sitting idle for the past 2 years.

I put in a new plug and it starts right up. This has the attached electric start feature and lo and behold I did find the original charger and owner manual. Was
thinking of cleaning it up and maybe selling it but now I may want to keep it for myself! Feels like a all-steel deck, very sturdy.

B) I am having trouble adjusting the cutting height levers in the rear, not sure why. Is there a secret to this?

C) Anyone venture a rough range selling value on this item?

Thanks in advance for any help.
Pete H.
Wisconsin

HRX models have a Nexite deck; hard plastic like a crash helmet. Lifetime warranty.

I picked one up last year for free at our town's throw-away day. Love it. I sent an email to Honda in order to find out when it was made. Got back to me within a day or so.

https://powerequipment.honda.com/support/contact-us

Are the back wheel levers just too tight or is it something more? If tight try some penetrating fluid & work them real good.

Value? Don't really know; I never see used ones for sale around here. But as you probably know, Home Depot's cheapest HRX217 is about $600 before tax & the electric start, roto-stop version is $850. Tax here would add another 80 to that.

thank you JBtoro! All helpful info. I have the cutting height adjusters loosened up. Also emailed Honda as suggested regarding the age. If I can just get the blades off to sharpen all will be well.
Trying some penetrating oil on the bolt heads first. Thinking I will be keeping this mower as a backup, it's too nice to sell.

I have 2019 HRX with the 200cc engine. My rear wheel adjusters are a nightmare to adjust. Even with the rear end off the ground, they barely want to move.