A friend of mine who posts on this site saw your question about Mobile cancels and passed it on to me. He suggested I join and reply, so here I am. I've been collecting Mobile for a long time and have catalogued over 350 dated examples before 1860, over 200 of which I own. The largest percentage are stampless.
You have received some great replies already so I don't know what I can add at this point, but I'll try.
A brief History of the Mobile CDS
There are at least 11 different Mobile CDS before 1860. The first were used during the late territorial period and into the early statehood period, about 1827, and were black. After that, red and blue began to also be used. It is believed that blue designated unpaid and red designated prepaid postage. As noted by others here, Mobile apparently did not like to have to apply the bar grid cancel to a stamped letter. They reverted back to using their CDS as town cancel and killer about the time the 1851 series of stamps came out.
They also stopped using blue ink and began using black ink for their CDS on domestic mail, with red being used occasionally for stampless and for most foreign mail. The latest use of red on domestic mail I have seen is 9/27/1852, on a stampless. After that, all Mobile cancels I've seen are black for domestic (and some foreign mail) and red for foreign mail.
The predominant Mobile CDS used on stamps between 1851 and 1858 are:
Prior to 1854;31mm;Ala.below
1856-1857;31mm;ALA.(small LA) after Mobile;12/28/1856
1850-1853, A very similar cancel;33mm; Ala. after Mobile and with a rate numeral below the date
From the photos in your post, I'd say the first and third ones are foreign usages but without seeing a rate number or the "Ala." "ALA.", what year range is guess work. But, because the letters of MOBILE are relatively close together, they look to me like the smaller 1856-1857 cancels.
I hope this adds some information for you. Mobile is great topic, lots of color and variety in the cancels and lots of good stories.