1 yes
2 not really. Rarity uses it mostly to get raw materials for her fashion creations
3 light show is just some minor illusions Rarity can use to add some flair to her fashion shows.
As for the others, It's been 2 seasons since that list was made... let's see...
Cloud Walking - it simply allows non-pegasi to walk on clouds. Do we have any locations that are normally pegasi-only?
Telekinesis - all unicorns have basic telekinesis. I assume this is telekinesis on the scale Twilight uses.
dragonfire - Spike can breathe fire as a combat move, but he can also use it to send small items (usually deliver letters to the princesses)
Spells not on your list that have appeared since:
bestow moustache - researched by Twilight after she needed (and lacked) one in her first adventure. No idea if it could have any practical use. Perhaps it could be used to aid evading monsters, or as a dud spell to randomly waste a spell draw.
polymorph - Twilight can transform her whole group, but it takes a moment and requires the target form creature to be available for use as a template.
conjure crystals - can be used to encease an enemy in a crystalline shell, or as an utility spell
force bubble - can protect the whole group from many forms of attack. It can also bar enyone from entering the location the caster is in
force barrier - it doesn't lock out a location, but it too can protect the whole party
summon item - an utility spell mostly, unless you summon a door to slam in the monster's face. Rarity uses it to summon a coach to dramatically faint onto
summon monster - used by Twilight once, bringing in a paraspryte to stop Trixie's pie attack.
mend - can be used to repair even large objects, like a breaking dam
time travel - brings the caster into a point in the past for about a minute, allowing her to witness a past event (trying to influence the past creates a stable time loop - However, the synopsis of season 5 finale indicates that there exists a more powerful version of the spell, capable of causing permanent changes. We'll have to wait)
bestow wings - grants a non pegasi an ability to fly - the wings are very fragile however
conjure snow - a variation of weather control useb by Trixie when under influence of the alicorn amulet - it's like a kid-friendly obedient avalanche.
fleshwarp - used by Trixie when under influence of the alicorn amulet, to comically disfigure the target.
age spell - used by Trixie when under influence of the alicorn amulet to temporarily age or de-age her targets, Stated to be very difficult.
orange morph - Twilight once tried to turn an apple into an orange - as it turned out, it can be used as baleful polymorph.
unmark - used by Starlight Glimmer to steal her victims' cutie marks. No idea if it could have any practical use for the characters.
