I am leveling from 10 in WotLK and I noticed the minimum level use of food and potions is 27, why is that?
I want to level the profession a bit and use it during leveling but I need to wait until 27.
They never adjusted the level requirements for crafted items in the expansion areas. Wrath professions started at level 70; post-squish that equates to level 27. That was broken even before Chromie Time - you could go to Northrend at 60 but you wouldn’t be able to use any crafted items until 70.
The only professions you can get any benefit from at level 10 are the vanilla professions, the rest you’ll have to wait until you hit a character level equivalent to what used to be the starting level for that expansion.
My newest alt is loving having to wait until 35 to learn the professions for where she’s leveling. She’ll be able learn the mining when she’s almost done with the continent and will have to go back for engineering instead of doing it while leveling 
Apparent intended method for leveling characters in SL: Don’t even bother with professions until you cap and then go back for what you want. Even grabbing double gather you’re stuck with default 0 skill until the required level and can learn it. Sure, you can gather it, but they’ll award you no points and not have mercy on your soul.
The relics of the past (crafters marks in SL speak) is suppose to allow you to scale down or up an item. The requirements to craft and then add one of these to a piece of gear feels a little excessive/expensive.
In order to craft just 1 you need some leather/cloth/bar from the particular expansion and some shadowlands trade goods (curing salt, penumbra thread etc). These trade goods cost 9 gold each. So a starting playing wanting to wear a level 14 piece of crafted gear has to shell out 9 gold per piece of gear. Not to mention you need to have at least 40 skill points in that expansions profession to even use said relic of the past on your desired gear.
Can you please change how this works blizzard? Could you change it so each relic requires a specific expansion trade good?
For example:
Relic of the past 1: Vanilla / BC trade good (example rune thread)
Relic of the past 2: WOTLK / Cata trade good (example eternium thread)
Relic of the past 3: Panda/WOD tradegood (couldnt find an example)
Relic of the past 4: Legion Trade good (Runic Catgut)
Relic of the past 5: BFA trade good (nylon thread)
Plus remove the rank 40 requirement to unlock the ability to add these relics while crafting said items?
On the bright side, the time from lvl 10 to lvl 27 is about 32 minutes. 
That’s actually not unusual. For some weird reason, Blizzard decided with SL that making lower level gear is actually more difficult. They placed the Novice Crafters Mark, which lowers gear to level 50, after the Crafters Mark 1, which lowers the gear to 55 (and the blue SL crafted gear defaults to 60 without any mark). And they specifically hotfixed it for several professions to ensure that the Novice Mark is learned strictly after Crafters Mark 1. So Blizzard very intentionally wants crafting lower-level gear to require more skill.
/boggle