Can I reverse bias the base-emitter of a BJT transistor?
The BE junction can be reverse biased, and your PNP will be off. The limit is the BE-junction breakdown voltage, as for any PN junction.

As long as you don't exceed that breakdown voltage, you'll be safe. The maximum reverse voltage the BE junction can withstand is usually listed in the datasheet in the Absolute Maximum Ratings section.

Here follows an excerpt from the datasheet of a jellybean PN2222 BJT (a "newer" version of the "famous" 2N2222):





And this is an excerpt from the datasheet of a PNP transistor of comparable (but complementary) characteristics (PN2907 - Fairchild):





Note, in general, that the limit is fairly low (5V..8V usually, even for power transistors), which is a strong hint that reversing the bias of the BE junction of a BJT is a risky business. So, unless you know exactly what you are doing, it is better to avoid reversing the bias of the BE junction for more than 1-2V.