Won't start up

check in the manual and see if it's self oiling or not,, some
machine parts are soaked in oil from the factory & don't need
to be oiled other machines have to be oiled,,if the manual doesn't
say then contact elna customer service and ask them.
I won't promise the machine will work or won't work if it's been
sitting for years ,sometimes the grease can become sticky and
hard.
you'll be able to tell as soon as you start sewing, make sure you
read the manual completely, that way you know what the machine
will do and what it won't do.
always use the proper needle for the fabric
and the proper foot
if you go over a seam and the machine seems to struggle, take your
foot off the foot pedal and use the handwheel to move the needle
manually over the seam, that way you don't bend a needle and cause
the machine to jump time.
also make sure to have a comfortable chair and good lighting and
a good seam ripper just in case of a mistake.
if you get frustrated while sewing, get up and walk around, that can
help clear your mind, I've had to do that plenty of times and I've
been sewing for 30 years.
if you don't have a manual send me a comment and I'll try to find you one.
there are several websites that have tutorials and other things for
a quilter,,
happy sewing

then you need to call the shop that serviced the machine & tell them
about the problem that the machine won't backstitch & see what they
say

sounds like a part is damaged or jamed, the machine needs to be checked
to see what's wrong with it

is it possible that the needles are in backwards?
it's very possible that the machine is out of time & would have to be taken to a sewing machine repair shop to be retimed

since the machine has been setting for 20 years, it needs to be serviced
the old grease & oil have probably turned the gunk. the servicing can also tell if any parts are damaged

if you have a manual check where your feed dog knob is, push the knob in the opposite direction,,if that doesn't help then something may be wrong with the feed dogs,,you should be able to see the feed dogs in the needle plate area & to feel them with your fingers.
you may need to have the machine serviced at a sewing shop

have you checked the needle to make sure it's in correctly--flat side of needle goes to the back of the machine

correct needle insertion is mandatory for the proper use in your sewing machine. Raise the needle bar to the highest point, then loosen the needle clamp screw to remove the old needle.
place the new needle in the needle clamp with the flat side of the needle facing the back (or if using a round needle the groove in the needle should be facing away from the shaft.
push the needle all the way up to the stop, or as far as it will go, then tighten the needle clamp screw.

how to decide which needle is correct to sew with, it depends on the fabric & thread being used for the project.
like for example, I've been sewing for over 30 years, I'm sewing a stretchy fabric & regular needles won't work because they skip stitches & will pull the fabric thus damaging the fabric, the needle I have to use is a singer universal ball point needles, & I have no problem with the stitches they come out fine.

as for the hand wheel not not being able to turn, it's possible that something could be loose or broken

you said it's been sitting for several years,, I would suggest that the machine needs to be serviced
by a sewing machine repair shop, where they can check the handwheel & find out why it won't unlock, & that the gears & inside the machine can be checked & grease & oiled & the timing check also

Try a new needle first failing that you may need to retime the machine, you can email me for an attachment of instructions [email protected]

it sounds like the take up lever has either come loose or is broken, & since the needle won't go up & down it needs to be checked