Pink sheets are OTC but they are not OTCBB. That is:

The Over-the-Counter Bulletin Board (OTCBB) is an electronic system that displays over-the-counter securities with real-time quotes and volume information. Shares listed on the OTCBB carry an "OB" suffix and must file financial statements with the Securities and Exchange Commission (SEC).1?
Shares trading on the pink sheet platform have a "PK" suffix and are under no requirements from the SEC to file financial information. For this reason, they are seen as high-risk investments.

The OTC Markets Group platform is segregated into 3 distinct market tiers: the OTCQX, the OTCQB, and the Pink. Each of these different tiers is separated based on perceived risk levels, which depend on the quality and regularity of a listed company's reporting information and disclosures.

Understanding Pink Sheets
Historically, pink sheets got their name from the color of the paper on which quotes of share prices were published. Today's trades are, of course, electronic, but the name lives on as a reference to OTC stocks.

Over-the-counter (OTC) refers to the process of trading for the securities of unlisted companies. The shares trade via a broker-dealer network rather than on a centralized stock exchange.

Pink sheets are OTC but they are not OTCBB. That is:

The Over-the-Counter Bulletin Board (OTCBB) is an electronic system that displays over-the-counter securities with real-time quotes and volume information. Shares listed on the OTCBB carry an "OB" suffix and must file financial statements with the Securities and Exchange Commission (SEC).1?
Shares trading on the pink sheet platform have a "PK" suffix and are under no requirements from the SEC to file financial information. For this reason, they are seen as high-risk investments.

OTCQB - includes the securities of companies that are current in their reporting to the SEC or a U.S. bank, thrift or insurance regulator;

OTCQX - reserved for the securities of companies that are current in their reporting to the SEC or a U.S. bank, thrift or insurance regulator, or, in the case of companies that are not required to report to the SEC, meet and remain current in their reporting obligations to OTC Link under its proprietary Alternative Reporting Standard; meet certain eligibility requirements; have audited financial statements; and partner with a third-party securities attorney or investment bank that reviews disclosure and acts as a professional advisor; and

OTC Pink - an open marketplace for a broad spectrum of equity securities, with no financial standards or reporting requirements.

OTC Markets Data products deliver information and insight on the 11,000 global and U.S. securities that trade on OTC Link ATS. As the primary market operator, we deliver the most comprehensive, contextual, real-time data on OTCQX, OTCQB and Pink securities.

No, it’s not. In addition, a Form 15 cannot be filed for a class of securities until on or after the Form 25 striking such class of securities from the relevant exchange (Nasdaq) has become effective. The Form 25 was filed and CACH was booted from the Nasdaq in 2015, so no form 15 whatsoever, where is it?

If the issuer has a class of securities
registered under Section 12(b), then either the issuer or
the national securities exchange must file a Form 25 to
initiate the delisting/deregistration process.