Is the Math Guide Online mobile friendly? Yes, although some images will probably benefit from the occasional zoom.
Will I be charged until I cancel? No. This membership does not renew automatically. If you wish to continue access past the date of expiration, you may purchase an additional 1-month or 3-month membership.
Is this the same as the paperback Math Guide? Mostly. I actually consider it to be edition 4.5, as I have made some improvements since the publication of the 4th edition. As I work towards publication of the 5th edition, the online version will remain synced with 5th edition.
If I purchase this in February, do I get a shorter subscription that someone who purchases in January? No. A 1-month subscription is always 31 days, and a 3-month subscription is always 93 days.