Interstate Issues: Multistate Guardianship in California and Wa

My question involves a child custody case from the States of California and Washington. The child (16) and parent live in CA, and we are relatives residing in WA, considering seeking guardianship. If it is relevant, she was adopted while she lived in WA. My logistical questions are:

• Do we have to seek guardianship in both states?
• If we hire legal counsel, should we hire in one or both states, or are there those who work in or specialize in interstate custody matters?
• Once guardianship is established, are we governed by WA or CA law or both? E.g. it appears that guardians can seek child support in CA but not WA, and one state may require annual reports.
• At what point in the process is the child allowed to move out of state? Will they and/or us need to return to CA for court during the process?

Thanks in advance.

Interstate Issues: Multistate Guardianship in California and Wa