In order of your questions: Not exactly, No, and No.
1. You don't lose feats, although some of them may become unusable.
The bonus feat you received for being a human is not lost. Under the description of feats:
A character can't use a feat if he loses a prerequisite, but he does not lose the feat itself. If, at a later time, he regains the lost prerequisite, he immediately regains full use of the feat that prerequisite enables.
In Pathfinder, the polymorph effect causes a creature to take on the physical form of another creature, but it does not fully "become" that creature. A human polymorphed into a squirrel is still technically a human. I strongly suggest reading through the full description of what is changed by a Polymorph effect.
2. Polymorphing does not inherently change your race, and so racial bonuses are not necessarily lost.
While under the effects of a polymorph spell, you lose all extraordinary and supernatural abilities that depend on your original form (such as keen senses, scent, and darkvision), as well as any natural attacks and movement types possessed by your original form. You also lose any class features that depend upon form, but those that allow you to add features (such as sorcerers that can grow claws) still function.
The human's Bonus Feat racial trait, Skilled racial trait, and +2 racial bonus all remain, because none of them meet the criteria above. While polymorphed, you are still inherently a human, even though you don't look like one. You will temporarily lose access to your 30 foot movement speed, and replace it with the movement speed(s) of your new form.
Your ability scores are not modified by this change unless noted by the spell.
Your character's Strength, Dexterity, and Constitution may be temporarily adjusted with Size bonuses. The rules page that I linked has a table with these adjustments, although these bonuses may depend by the source of the Polymorph effect. Usually, growing tends to cause Size bonuses to Strength and Size penalties to Dexterity, and shrinking tends to do the opposite.
For comparison, take a look at the Reincarnate spell; it actually does change a creature's race, causing them to change their racial ability score modifiers.
3. Polymorphing does not cause you to gain any feats.
The creature's bestiary page refers to a typical version of that creature; you won't acquire the squirrel's feats just by polymorphing into one.
A polymorph spell transforms your physical body to take on the shape of another creature. While these spells make you appear to be the creature, granting you a +10 bonus on Disguise skill checks, they do not grant you all of the abilities and powers of the creature.
The squirrel's racial bonus feats exist because it is inherently a squirrel. If the squirrel was polymorphed into a human form, it would have its original feats, ability scores, and skills. Due to the size increase, its Strength would get a Size bonus and its Dexterity would get a Size penalty.