IPL Laser Side Effects - When do They Go Away?

I am sorry to hear that you have had some complications from IPL. In general, when performed by an experienced provider IPL is extremely safe and well tolerated. However, there are some real complications that can occur if people are not cautious and start conservative with treatment parameters. 
It sounds like you have a couple different issues going on. First, the areas of hyperpigmentation are likely PIH (post-inflammatory hyperpigmentation). Depending on how recent these are I will initially treat this with topical steroid creams, but this is usually only effective within the first few days and weeks after the pigment occurs. Sometimes enough time will improve them but if not any better after a few months I prefer using one or a combination of topical lightening creams, microneedling, PRP, and fractional laser.
The areas of hypopigmentation (white areas) sound like either scars which unfortunately are more difficult to treat, or potentially simply areas that were overrated and lost some natural pigment.  If it is the latter then time may be all that is needed for the pigment to come back (can take months or years) or sometimes additional laser around the areas to even out the skin can help. If it is true scarring then multiple treatments with microneelding, ablative and non-ablative fractional laser, and sometimes topical brimatoprost can help reduce the scar and improve the color.
In regards to the changes in your neck, it is difficult to say. IPL does not changes volume or skin laxity/elasticity. I would just recommend watching that for now.

Older IPL systems have a low threshold between effective treatment and a facial burn.  A burn can result in transient tiger striping, hyperpigmentation or can result in much harder issues to resolve such as hypopigmentation or scarring. Newer IPL systems are much more powerful but targeted in their delivery system and less likely to cause these issues, particularly coupled with a reputable aesthetic physician's office.

Sciton® BBL technology treats sun-damaged and
aging skin effectively. The light energy delivered by the BBL will gently be
absorbed by the unwanted melanin responsible for pigmented lesions in the upper
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spot-treat superficial resurfacing. Red veins will simply disappear!   Pigmentation is not scarring and can be remedied with the BBL by a skilled provider.#BBLtreatments   #lowrisklasers   #BBLsideeffects