When changing a vesting schedule, are all these statements true?

[John A]

I believe all of the following statements are true regarding changing a vesting schedule. Does anyone disagree?

Any participant with 3 years of service must be given the choice as to which schedule to vest under.

The vesting percentage of a participant cannot ever be lowered by a change in vesting schedule.

The new vesting schedule can apply to all new participants if the amendment changing the vesting schedule is worded that way.

The plan amendment may provide for whichever schedule give the participant a higher vesting percentage in each year, but is not required to.

A plan can adopt an amendment that specifically states that any employer contribution made after the effective date of the amendment would vest under the new schedule, regardless of the participant's vesting percentage under the old schedule (or at least, no guidance specifically prevents it).