Then of course you have all sorts of questions if you use the books rules...
Keep in mind that Magic is a very broad topic, and the rulebook is already huge without legislating the particulars of every possible interaction. The rules often presume GM will have to abritrate, and the Perceiving Magic rules are no different. But to provide what I consider to be reasonable answers to your hypothetical scenarios:
Q1) I'm sustaining a Heal spell on a sore leg and someome walks past my motel room do the wall and wooden door prevent them getting a check by providing full cover?
I doubt such a scenario would satisfy the "in the area" clause establishing relevancy of getting a perception check.
Q2) I'm sustaining a spell to translate another language walk into a cinema and sit next to someone they get a check after the lights go down someome comes in and sits on my other side do they get a harder check?
The rules of Perceiving Magic are making a Perception test. They say nothing about being immune to environmental modifiers to perception checks.
Q3) Related to 2 if your sustaining a force 8 spell and enter an area with a background count of 4 is it easier, harder or the same for people to detect the spell.
Depends on whether you're playing that BGCs lower the Force of the spell or the net hits. Lower Force=Harder to notice.
Q4) Is a force 6 spell able to be detected further away than a force 2 spell or is it just easier to notice.
Strictly by RAW just easier to notice. But again the "in the area" language is (imo intentionally) quite vague. GM isn't hamstrung and has authority to be flexible.
Q5) Is there a range limit e.g. can a spell be detected at 1m. 10m, 100m, 1000m?
Per paragraph 3 of the Perceiving Magic rules, some magic is blatant and no test is required. In those cases if you can see the mage, you can see the magic. Throwing a fireball at night can be seen for kilometers if LOS is clear. For the subtle magic where Skill-F/6-F is invoked, one must be "in the area", as defined by the GM.
Q6) Related to 5 is there a range penalty like there is for sounds so a spell is harder to detect at 10m than 1m?
The rules governing perception would be in full force as the rules for Perceiving Magic don't invoke a sort of special Perception test where the modifiers are ignored. The rule only establishes a mechanic for setting a threshold and adds a special modifier for the case of the observer having a magic related active or knowledge skill. If a GM is saying "in the area" is a big enough area for sound to die off, then sure that'd apply. Note also there's the +3 bonus if the observer is looking for magic specifically.
Q7) What about adepts if one has a +4 to strength from a power can that be detected in this way?
The only magic that doesn't fall under "all magic", per implication by the book's explanation of the rule, is magic that both is not blatant (invoking paragraph 3) and lacks a Force value (paragraph 2 only governs magic with F values).
Q8) Is there a penalty from distractions e.g. their watching the latest episode of a series in Ar?
If you're gonna say being distracted by the Trid penalizes perception tests and noticing magic is a perception test, then why wouldn't it be penalized?
Q9) Why do sustained spells get easier to notice from force 1 to force 5 them plateu with no difference between a force 6 and (if anyone could cast it) a force 60 spell?
Because Force 6+ is the magical equivalent of un-concealable gear? Yet in the case of magic, even the hypothetical Force 60 still has a Threshold of 1 meaning it's possible it could be missed.
There are wards that are created without skills involved: Building a lodge for example.
The example didn't specify, and applies to "Wards". Would you be comfortable saying that the example "clearly meant" Wards created without skills and Wards that were created via Ritual Spellcasting go Skill-F instead? Or that Wards created by Ritual Spellcasting are imperceptible since the act of "performing" is no longer in effect?